This Is the Reason the S&P 500 Fell Off a Cliff Today

The market melt-up got replaced by a ham sandwich today after both Caterpillar (NYSE: CAT) and Greece combined to put the optimists back in their cage -- at least for a day. The broader market S&P 500 (INDEX: ^GSPC) finished the day lower by 15.30 points (1.05%) to 1441.59.

Leading the charge lower was a tepid growth forecast through 2015 from heavy-duty manufacturing giant Caterpillar. As a mainstay of the manufacturing sector, its slow-growth forecast and primary focus on cost control bode poorly for global growth.

Greece's problems are also never-ending. The highly indebted nation may need to ask its eurozone partners to roll over tens of billions in debt; otherwise, it may need to borrow more money at market rates by as early as 2015 to cover its interest payments.

Let's have a quick glance at a few other companies moving the S&P 500 in a big way today.

Not surprisingly, one of Caterpillar's biggest competitors, Joy Global (NYSE: JOY) , had a miserable day, losing 5.5%. Joy makes equipment that mining companies use to get metals and resources out of the ground. If Caterpillar's forecast rings true, then Joy's three-to-five year outlook may include weak growth prospects as well. It also doesn't help that Joy is fairly dependent on the health of the coal sector to drive heavy-machinery sales, and coal prices have been anything but strong recently.

Office-supply chain Staples (Nasdaq: SPLS) was clipped as well, shedding 4.5%, after outlining plans to speed up the closure of 15 stores in the U.S. by the end of the year and close 45 stores in Europe. The resulting charge from the store closures is expected to affect earnings negatively by $35 million. Staples plans to instead focus its efforts on its online and mobile business, as well as expand its product offerings for small and large businesses. Although it won't be easy, I recently highlighted why I think Staples could be a unique turnaround play.

It wasn't doom and gloom for all 500 companies, however, as grocer Safeway (NYSE: SWY) bucked the trend in a big way -- up 2.6%. Earlier today, BMO Capital Markets upgraded Safeway to "outperform" from "market perform," citing the recent success of its "Just for U" personalized digital couponing plan as the reason for the brighter outlook. Safeway still isn't out of the woods, as rising food costs are straining already thin margins, but connecting with consumers through personalized coupons is a strategically smart move that could go a long way.

Did you catch the number of that dump truck?Should Caterpillar's growth forecast send investors scurrying for a cave to hide in? Find out the answer to this question and much more by getting your copy of our latest premium research report on Caterpillar. Packed with in-depth and unbiased analysis on the opportunities and threats facing Caterpillar, and complete with a year of regular updates, this report will give you the edge needed to make smart long-term investing decisions. Click here to get your copy.

Fool contributorSean Williamshas no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen nameTMFUltraLong, track every pick he makes under the screen nameTrackUltraLong, and check him out on Twitter, where he goes by the handle@TMFUltraLong.

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